1. Introduction
This invention pertains to an intravaginal alarm for predicting and detecting parturition and detecting the related events of fetal readiness and fetal stress syndrome in mammalian animals. The invention also pertains to methods for detecting these events.
2. Description of the Prior Art
The inability to detect the onset of parturition has proved to be a dilemma to both humans and animal husbandmen. It is not uncommon for women to unexpectedly give birth before arriving at a medical facility, and the occurrence of false labor, and the inconveniences related thereto, are commonplace. The problems are even greater for the animal husbandman, who must attempt to determine the onset of parturition without the aid of intelligent input from the animal herself. For the animal husbandman, it is also difficult to detect the onset of parturition by an animal unless the animal is under constant surveillance.
Researchers in the past have noted subtle changes in activity and appearance of an expectant female within about two weeks of parturition but these subtleties are not universal among animals of the same species nor are they necessarily similar from one species to the next. Numerous attempts at detecting the onset of parturition by noting such subtleties have accordingly failed. Exemplary of such failures is a study reported by R. Ewbank entitled "Predicting the Time of Parturition In the Normal Cow: A Study of the Pre-Calving Drop in Body Temperature in Relation to the External Signs of Imminent Calving,", presented at Vet. Rec. 75:367-371 (1963), in which the monitoring of subtle changes in 21 female cows led the researchers to believe that nine of the cows, which calved within two to twelve hours, were not expected to calve and six other cows, which failed to calve within the succeeding twelve hours, were expected to undergo imminent parturition.
As a result of the failure of the livestock industry to establish a suitable test regimen for the determination of the onset of parturition by changes in activity and appearance of the female, direct 24-hour observation by farm personnel has typically been the only dependable means of insuring that an expectant female receive appropriate assistance at the time of delivery. As stated by one writer, "While it is possible to predict the time of calving within a day or so, advanced prediction of calving time to within an hour or so is impossible. As a result, repeated checking of animals known to be near parturition is one of the only ways to determine the exact time of birth. This can be a timeconsuming process and it runs the risk that not only may the birth occur undetected, but also that the farmer may become involved too early and cause injury to the cow or calf by rushing the process." Scott et al, "Electronic Developments in Dairy Herd Management," Proc. of the Symp. Automation in Dairying, Wageningen, the Netherlands, pp. 221-236 (1983). Regarding sows, another writer commented, "Because farrowings in the normal way do occur at all hours of the night and day and gestation periods can vary in length from one sow to the next by several days, precise scheduling of personnel for supervision can be costly and difficult and perhaps even impossible to arrange unless the time of parturition can be closely controlled." Gordon, Controlled Breeding in Farm Animals, copyright 1983 by Pergamon Press, New York, N.Y. p. 333.
Despite the admonitions of writers in the art that, when the onset of parturition is to be detected by direct observation, monitoring personnel be available at all hours of the day, budgetary concerns and practical difficulties have caused many farm managers who rely on direct observation techniques to provide only partial monitoring of the expectant females. The result is a high mortality rate for the offspring. In the New Mexico State University dairy herd, nearly 10 percent of the calves are listed as dean-on-arrival, a statistic almost completely due to nighttime births which are unattended. Other researchers have found that the mortality rate for calves involved in difficult births is four times higher than for those born without difficulty and that, of calves dead at birth, approximately 90 percent of the losses are attributable to delays in receiving assistance or the amount of difficulty and time required to remove the calf. Laster et al, "Factors Influencing Peri-and Early Post-Natal Calf Mortality," J. Anim. Sci. 37:1092-1097 (1973). Another writer reports that cattle experience dystocia (difficult birth) in 30 to 60 percent of births in primiparous dams, in 8 to 25 percent of second calf births, and in 2 to 8 percent of births to mature dams, and that as many as 70 percent of the calves lost at parturition have functional lungs, indicating that they were not stillborn but rather died as a result of injuries and physiologic trauma during prolonged and difficult delivery, problems that could normally have been overcome if monitoring personnel had been present. Hafez, Reproduction in Farm Animals, Fourth Edition, copyright 1980 by Lea and Febiger, Philadelphia, Penna. p. 340.
Losses resulting from the failure to provide constant monitoring, when direct observation is the only means of detecting the onset of parturition, are not limited to the cattle industry. In a study involving more than 150 supervised farrowings, the loss of all piglets from birth to weaning was reduced to less than six percent during a period of close supervision, in contrast to a loss of more than 20 percent in the same herd before and after the period of supervision. Dziuk, "Control and Mechanics of Parturition In the Pig," Anim. Reprod. Sci., 2:335-342 (1979). Other research has demonstrated that resuscitation of a substantial proportion of apparently dead piglets is possible. Milosavljevic et al, "The Revival of Apparently Stillborn Piglets," Acta. Vet. Beograd., 22:71-76 (1972). Without close supervision, it has been estimated that losses in the United States alone of piglets near birth is about 22,000,000 annually, a figure that exceeds death loss from transmissible gastroenteritis, the dramatic killer of piglets, by about 19 times, and exceeds by a factor of several times all other death losses from disease and management combined. Dziuk, supra. With regard to horses, it has been found that 83.6 percent of horse foalings occurred at night with the great majority coming within two hours before or after midnight, such that the failure to monitor expectant mothers during this period can result in death or serious complications. Finally, even though human females have attempted to counteract the problem by obtaining professional advice on a frequent basis and by reporting to a hospital at the first sign of parturition, many false starts and emergency runs occur due to the inadequacy of reliance upon subjectively observable changes.
Others in the prior art have appreciated the inadequacy of directly monitoring changes in expectant farm animals to determine the onset of parturition and, accordingly, a number of devices have been suggested for making the determination. The devices generally attempt to determine the onset of parturition by automatically detecting bodily conditions commonly associated therewith. Thus, devices have been developed for detecting tail raising in cows and horses, lying prone in horses, increased heart rate in horses, and fetal water bag swelling in sheep. The devices are unsatisfactory because, inter alia, they are subject to false alarms, they are limited to a particular family or families of animals, and/or they require considerable maintenance. Also, in the case of the device used to detect fetal water bag swelling in sheep, which involves the precise intravaginal insertion of a thermister probe that senses a temperature difference upon explusion, the device is incapable of being retained by the animal for extended periods of time, causes an increased liklihood of infection and infestation by screw worm larvae, and causes stress and discomfort. Finger et al, Erste Mitteilung uber Entwicklung und Einsatz eines elktronischen Geburtswachters fur Schafe, Berl. Munch. Tierarztl. Wschr., 95:130-132 (1982).
The devices disclosed in U.S. Pat. No. 3,583,389, issued to Harvey, and U.S. Pat. No. 4,028,687, issued to Hamaguchi are similar to the intravaginal parturition device for sheep, disclosed in the Finger reference, supra, in that they are designed to be inserted into an animal's vagina and expulsed at parturition, whereupon a signal is generated. In the Harvey patent, an egg-shaped device is disclosed that is particularly adapted for use in sows. The device is provided with a transmitter that is energized or deenergized in response to the attainment of a predetermined temperature. Upon expulsion of the device from the vaginal cavity, the transmitter is activated to transmit a signal that in turn activates a warning system such as an audible sound or a light. In the Hamaguchi et al reference, the device is similarily actuated upon expulsion from the vaginal cavity, but the actuation is in the form of the generation of an electric current that is shorted out while the device is located intravaginally. Like the Harvey invention, that of the Hamaguchi et al device is generally egg-shaped but, in one form, is provided with an elastic annular projection to assist in the retention of the device within the vagina. While in some respects the Harvey and Hamaguchi et al inventions may be improvements over the prior art, they do not provide a complete solution to the problem.
Aside from the use of the temperature change upon explusion of an object from a reproductive tract as an indicator of parturition, others have attempted without success to show a reliable relationship between temperature phenomena and the onset of parturition and related events. Eight research reports have been summarized as describing a body temperature increase during the latter part of pregnancy with a substantial drop during the last few days to a few hours before parturition. Ewbank, Vet.Rec. 75:367-371, supra. A brief mention of a temperature drop in dogs about one day before parturition has more recently been recorded. Cole et al, Reproduction in Domestic Animals, Third Edition, copyright 1977 by Academic Press, New York, N.Y. p. 517; Tsutsui et al, "Variations in Body Temperature in the Late Stages of Pregnancy and Parturition in Bitches," Jpn.J. Vet.Sci., 44:571-576 (1982).
However, for a number of reasons, the efforts of workers in the field to develop a reliable relationship between temperature phenomena and the onset of parturition have failed. In fact, the prior art would actually lead one away from the use of temperature measurements as a reliable tool in the forecasting and identification of occurrences related to parturition. Researchers in the field generally reported failures in their attempts to use such measurements in forecasting and determining occurrences related to parturition, thus dissuading other researchers from further study. Additionally, with only one exception, no current textbooks on reproductive or general animal physiology have been found that comment on any temperature phenomenon related to parturition and, furthermore, even the prestigious reference book, The Merck Veterinary Manual, Fifth Edition, makes no mention of any species that have a temperature phenomenon associated with parturition.
Closely related to the failure of the prior art to effectively detect the onset of parturition is the failure of the prior art to detect the occurrence of fetal readiness. In order to determine the most optimum time to induce labor in mares, for example, attempts have been made to gauge fetal readiness by criteria that typically include the occurrence of a minimal estimated length of pregnancy (about eleven months, two weeks) and subjective opinions regarding the fullness of the teats, the looseness of the pelvis, and the position of the fetus. Because these criteria only imprecisely indicate an appropriate point at which the induction of labor is safe, there is a substantial risk to the fetus.
The prior art has also failed to satisfactorily determine the occurrence of fetal stress syndrome, which may occur during parturition. When fetal stress syndrome occurs, the fetus' temperature begins to climb dramatically, and the mother's temperature similarily undergoes a marked temperature increase. It is important to administer suitable treatment to remedy the problem as soon as possible in order to reduce the risk of fetal mortality or injury. Weisz, "The Temperature Phenomenon Before Parturition and Its Clinical Importance," J.A.V.M.A., 102:123 (1943). While the prior art has appreciated the importance of suitably administering treatment to the mother and fetus upon the occurrence of fetal stress syndrome, the prior art has failed to adequately provide a means for detecting the onset of fetal stress syndrome, such that the treatment can be immediately applied.
In view of the shortcomings of the prior art, it is an object of the present invention to provide an improved system and method for predicting the onset of parturition in a mammalian female.
It is a further object of the present invention to provide an improved system and method for detecting the onset of parturition in a mammalian female.
It is a further object of the present invention to provide an improved system and method for determining the attainment of fetal readiness for parturition in a mammalian female.
It is a further object of the present invention to provide an improved system and method for determining the occurrence of fetal stress syndrome in a mammalian female.
It is a still further object of the present invention to provide a system and method for predicting the onset of parturition, and determining the occurrences of fetal readiness, the onset of parturition, and fetal stress syndrome, that can be adapted for a number of families of mammalian females with minor modifications and are accurate, reliable, safe, convenient and economical.
Other objectives of the present invention will be apparent from the following detailed description of the preferred embodiments.